Burmese fishermen raise their hands as they are asked who among them wants to go home at the compound of Pusaka Benjina Resources fishing company in Benjina, Aru Islands, Indonesia.
Photograph: Dita Alangkara/AP

The global movement against human exploitation is being driven by a relentless search for statistics. This obsession with data is based on an untested and widely held assumption that if we can discover how many slaves there are in the world; if we can somehow rank each country’s response from worst to best, then we are closer to fixing the problem. But this is a trap that is sucking up resources, expertise and energy, stifling the imagination and innovation needed to expose the structures that nurture modern slavery.

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The 2016 sustainable development goals commit member states to eradicating trafficking and modern slavery. Country-level progress towards implementation of this commitment will be measured with reference to: the “number of victims of human trafficking per 100,000 population, by sex, age group and form of exploitation”.

But what does all this data tell us? First of all, at least in relation to country-level prevalence, the figures are probably way off. As I explain in my analysis of the methodology used for the 2016 Global Slavery Index, we don’t yet have the definitions or tools to calculate the size of the problem in a reliable and replicable way.

Even if we were able to measure crude numbers, these provide no context. They tell us very little about the situation of the individuals enslaved; what needs to be done to help them; and how legal responsibility for their plight should be apportioned.

Beyond being forced to endure a miserable existence, a Yazidi girl forced into sexual slavery by Islamic State has little in common with a Rohingya asylum seeker sold into forced labour on a Thai fishing boat. Both are worlds apart from a Hungarian woman forced into commercial sex work in the UK to pay off her recruitment debt. Each of these situations is the result of complex interplay between social, economic and political circumstances, which get lost when the focus is purely on the numbers.

Ranking individual countries according to the quality of their response is equally problematic. For one thing, assessment criteria used by both the US State Department Trafficking in Persons (TIP) Report and the Global Slavery Index contain an in-built bias towards wealthy countries.

It is expensive and difficult to do the many things required for a good grade: to identify victims quickly and accurately; to implement sophisticated support and protection programmes; to prosecute traffickers effectively. Of 31 countries that received the highest ranking in the 2015 TIP Report, only one developing country (Armenia) was included. The top three countries in the Global Slavery Index are the Netherlands, the US and the UK, and no developing countries make it into the top ten.

These rankings are not just distorted – they are also misleading because they fail, spectacularly, to tell us what is really happening. They fail to take account of the reality that wealthy countries benefit disproportionately from the goods and services produced through cheap and exploitable labour; that the supply chains of corporations owned and run by the nationals of top-ranked countries are tainted with slavery; and that corporate profits flowing back to these countries are vastly inflated by the cheap, exploitable labour that is often supplied by countries whose “anti-slavery” responses have been judged most wanting.

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Is there a better way to find out what we really need to know? Perhaps. Over the past few years, the anti-trafficking/anti-slavery movement has benefited enormously from forensic, sector or target-group specific analysis that seeks to unravel the threads that knit together a situation of exploitation.

Unfortunately, this kind of painstaking research and analysis is still too rare and too often in the hands of investigative journalists or underfunded private advocacy groups who don’t have the power to confront governments and the private sector over their complicity in trafficking and modern slavery.

The headlines and the funding remain firmly within the cult of quantitative data and statistics – even when this offers us so little depth and context.

That needs to change. Unless and until we learn, at the level of individuals and communities, what is really happening – and who is responsible – we cannot hope to challenge the structures that perpetuate the exploitation of human beings for private profit.

•Anne Gallagher is a lawyer, teacher and practitioner in criminal justice and human rights, and has been working on trafficking issues since 1998. In 2012 she received a Trafficking in Persons Hero award